Wireless Performance Question

[jcampos87]

I saw this statement made in an older posting:

"Given that one AP will never really push more than 18Mbps of real throughput anyway (yes, even if all clients are running at 54Mbps), I'd be surprised if you actually have any contention worth worrying about. "

Original link to posting:

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Wireless%20-%20Mobility&topic=Getting%20Started%20with%20Wireless&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.2cbea769/0#selected_message

Can someone explain to me how this number is achieved? What is the formuala? Also, what is the max throughput for a, b and g respectively?

Thank you

[pavanpujari]

The throughputs generally seen by AP for one 54 Mbps client does not ideally exceed beyond 18 Mbps (i have seen max throughputs of 22Mbps for TCP traffic). Though adding more clients at 54Mbps will definitely increase the contention thus increasing the backoff experienced by each station.

I am not sure if the throughputs vary for the QoS enabled APs and having traffic other than TCP. You can get the throughputs by calculating the MAC overheads and the transmission time for each TCP packets.(transmission time includes 2 TCP + ACKs, if delayed ack is turned on). This gives the transmission time for 2 TCP segments. The inverse of this gives you the transmission rate.

Hope this helped you.

Pavan